<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	<script>
		function SuperType () {
			this.property = true;
		}
		SuperType.prototype.getSuperValue = function(){
			return this.property;
		};

		function SubType () {
			this.subproperty = false;
		}

		SubType.prototype = new SuperType();

		SubType.prototype.getSubValue = function () {
			return this.Subproperty;
		}
		var instance = new SubType();
		alert(instance.getSuperValue()) // true
	</script>
</body>
</html>